Scottish international Robertson, 20, has cost the Tigers £2.85million while 21-year-old Maguire has joined for a £2.5million fee, according to the club's official website.

Both players have signed three-year deals, with the club having the option to extend their contracts by a further year.

Left-back Robertson was on a part-time contract with Queens Park in Scotland's third tier just over a year ago before Dundee United spotted his potential.

He arrived at Tannadice last summer and went on to make 44 appearances and be named the PFA Scotland young player of the year and be included in the team of the year.

Maguire, capped once by England under-21s, was Sheffield United's player of the year in each of the last three seasons during which he made 166 appearances.

As one left-back moved from Tannadice to Hull, another moved in the opposite direction as 21-year-old Conor Townsend joined the Scottish Premiership club on a season-long loan.

The Hull academy graduate has spent time on loan at Grimsby, Chesterfield and Carlisle in recent seasons.

Dundee United manager Jackie McNamara told the club's official website: "I was delighted to secure Conor so quickly. It was important to get him in early so he can settle in before the start of the competitive action.

"He is a really good defender who will do a job here. His athleticism and height will enhance our squad."